Alternating current buzzer



NOV. 21, 1939. J, A. ROSTRON 2,180,881

ALTERNATING CURRENT BUZZER Filed Sept. 24, 1957 bww/Rank fg-y om UNITEDPATENT QFFICE' .A n, ..7 .2,180,881 v i 5.-.' ALTE'I'G CURRENT BUzzEItJoseph A. Rostron, Cambridge, Mass.

Application September 24, 1937, Serial No. 165,540

3 Claims.

This invention relates to electric buzzers intended for operation byalternating electric current to produce a sound the frequency of whichis dependent upon the frequency of the current.

The buzzer is especially intended for use in houses to operate from thebell ringing transformer that is usually a part of the equipment of anelectrically equipped house.

One of the objects of the present invention is the provision of a buzzerthat is exceptionally simple in construction and inexpensive and is freefrom contacts and springs.

A further object of the invention is the provision of a buzzer whereinthe vibrating element is relatively massive and carries the magnetizingcoil that when energized causes the element to vibrate.

Another object of the invention is the provision of a buzzer having suchconstruction that the compartment containing the vibrating element canbe tightly sealed at the factory.

A further object is generally to improve the construction of electricbuzzers.

Fig. l is a plan view of the buzzer embodying the present invention.

Fig. 2 is a reverse View of the buzzer of Fig. 1 with the bottom coverplate partly broken away to illustrate the Vibrating element.

Fig. 3 is a sectional View taken along line 3-3 30 of Fig. l. f

The buzzer comprising the present invention comprises a casing IIJcomposed of magnetic material, as cast iron or a steel stamping, andpreferably although not necessarily, is of circular 35 configuration.The casing includes an upstanding boss I2 which has an annular flange I4outstanding at its bottom edge. The flange I4 is internally recessed toreceive a cover plate I6 of any suitable material, preferablynon-magnetic,

40 the cover plate being secured in position by hollow eyelets I8 whichprovide passages in which attaching screws, not shown, may be passed tosecure the buzzer to a support. The boss I2 is provided with an internalrecess 20 herein shown as circular in configuration and a deepercylindrical central recess 22, thereby providing an annular ledge 24surrounding the recess 22.

A vibrating element is located Within the recess 20. Said elementycomprises a magnetic bar 26 suitably of rectangular cnoss section andformed conveniently of what is known as cold rolled steel. Suitabledimensions for the bar for operation on sixty cycle alternating currentis a length of 2", a Width of l" and a thickness of 11e". Thesedimensions can be varied, how-v ever. A bar of this material of theWidth and thickness and short length herein employed is not commonlyconsidered springy material but has been found to be Well suited for thepresent 5 purpose. The bar is longer than the diameter of the recess 22so that it overlies diametrically opposite portions of the annular ledge24. Said bar is secured to the ledge at one end by a pair of clampingscrews 28 and 30 which are loosely ex-` 1()4 tended through the boss l2and are screwthreaded into the end of the bar. The end of the bar istapered as at 32 so as to provide a fulcrum 36 which bears on the ledge24 intermediate the screws 28 and 30. Thus by tight- 15 ening one screwand slackening off the other screw the spacing between the free end ofthe bar and the diametrically opposite part 25 of the ledge 24 can beadjusted while at the same time the clamped end of. the bar is heldrigid. 20

The bar carries a magnetizing coil 38 the terminals of which areconnected to the tWo binding posts 46 upstanding from the upper face ofand insulated from the boss I2 and by Which the coil can be connected toa source of alternating 25 current power.

Since the casing I 0 and the bar 26 are of magnetic material a closedmagnetic circuit is provided for the coil except at the air gap 42betweenA the free end of the bar 26 and the over- 30 lying portion 25 ofthe ledge 24. Thus the free end of the bar 2B is attracted toward theledge at each half cycle of the current wave and thus is caused tovibrate at twice the frequency of the alternating current. Thedimensions of the `35 bar and of the coil are adjusted .so that goodvibration is obtained. The amplitude of vibration is intended to vbesufficiently great to cause the free end of the vibrating bar to strikeagainst the part 25 of the ledge 24 at each vibration so as to 40produce a distinct sound over and above the sound produced by thevibration per se of the bar when the device is operated. The adjustingscrews 28 and 30 permit ready adjustment of the length of the air gap 42,either for initial adjustment of the device at the factory or forsubsequent adjustment for good operation on a different voltage. f

I claim: 50

1. An electric buzzer comprising a casing of magnetic material closed atthe top and open at the bottom and provided with opposed abutmentsconfronting the bottom opening, a resilient vibratory bar of magneticmaterial having onev end 55 clamped to one abutment and having itsfreely vibratory end overlying and adapted to vibrate against anotherpart of said abutment by reason o its own resiliency, a magnetizing coilsurrounding and carried by and vibrating With said bar between saidabutments, and a cover plate closing the bottom opening of said casingand attached thereto.

2. An alternating current buzzer comprising a casing `of magnetic.material having .opposed ledges and an intervening recess, a resilientvibratory bar of magnetic material traversing said recess and having itsone end clamped upon one ledge and its other end closely spaced fromsaid other ledge, and a magnetizing Winding surrounding and carried byand vibrating with said bar and at least partly located in said recess.

3. An alternating current buzzer comprising a cylindrical casing ofmagnetic material having an annular ledge surrounding a cylindricalrecess, a vibratory bar of magnetic material diametrically bridging saidrecess and having means clamping one end of said bar upon a part of saidannular ledge and having the opposite freely vibratory end of said..bar-closely confronting and adapted to vibrate..againstz.the diametricalopposite side of said ledge, and a magnetizing coil surrounding `andcarried by and vibrating with said bar in said recess.

JOSEPH A. ROSTRON.

